Color television degaussing means having a thermomagnetic core surrounding the face of the cathode ray tube



Dec. 5, 1967 G. G. MERKL ETAL 3,356,889

COLOR TELEVISION DEGAUSSING MEANS HAVING A THERMOMAGNETIC' CORE SURROUNDING THE FACE OF THE CATHOD E RAY TUBE Filed April 28, 1966 United States Patent 3,356,889 COLOR TELEVISION DEGAUSSING MEANS HAV- ING A THERMOMAGNETIC CORE SURROUND- ING THE FACE OF THE CATHODE RAY TUBE George G. Merkl, New Milford, N.J., and George B. Pearson, Douglaston, N.Y., assignors of twenty-five percent to Arthur L. Harrow, New York, N.Y.

Filed Apr. 28, 1966, Ser. No. 546,074 5 Claims. (Cl. 315-8) This invention relates generally to the field of television degaussers of the type in which magnetic field producing means surrounds the peripheral areas of the cathode ray tube, and more particularly to an improved form thereof having means for automatically tapering the magnetic field to a minimum during the period of time in which the television receiver is warming to operating temperature. Devices of this general type are known in the art, and the invention lies in specific constructional details permitting simplicity in manufacture, and improved reliability.

It is among the principal objects of the present invention to provide an improved degaussing means which will employ the thermomagnetic characteristics of certain metallic materials.

Another object of the invention lies in the provision of an improved degausser of the class described in which the cost of manufacture may be of a relatively low order, thereby permitting consequent wide sale, distribution and use.

A further object of the invention lies in the provision of an improved degaussing struture which will delay operation of the cathode ray tube until its function has been completed.

These objects, as well as other incidental ends and advantages, will more fully appear in the progress of the following disclosure, and be pointed out in the appended claims.

In the drawing, to which reference will be made in the specification, similar reference characters have been employed to designate corresponding parts of the plural embodiments disclosed.

FIGURE 1 is a schematic view of a first embodiment of the invention.

FIGURE 2 is a schematic view of a second embodiment of the invention.

FIGURE 3 is a schematic view of a third embodiment of the invention.

Referring to FIGURE 1 in the drawing, the first embodiment, generally indicated by reference character 10, includes a rectangularly shaped laminated metallic core 11 which surrounds the peripheries of a conventional cathode ray tube of a type used for color reception. The core is formed of any material which will exhibit thermomagnetic characteristics, that is to say the property of changing obtainable flux by varying ambient temperature conditions. The Nilvar family is particularly suited for this purpose, and I have found that an alloy consisting of 30% nickel and the remainder iron to function extremely well. As seen in FIGURE 1, the core 11 includes a first side member 13, a top member 14, a bottom member 15, a side member 16, and an auxiliary member 17. The members 13-16, inclusive, are surrounded by first, second, third, and fourth coils, 18, 19, 20 and 21, respectively, all of which are wired in series to the usual 117 volt alternating current source, generally indicated by reference character 22, including a push-button 23.

The auxiliary member 17 is provided with a delay coil 24, the function of which will be more fully explained hereinbelow, having leads 25 and 26 connected to a relay 27 having latching contacts 28.

The source 22 also connects through a power switch Patented Dec. 5, 1967 ICC 29 to the primary winding 30 of a power transformer 31 having a first secondary winding 32 providing filament heater voltage to the filaments to the tubes of the receiver (not shown). A secondary winding 33 provides plate voltage, and is wired in series to a second set of contacts 34 on the relay 27. Current from the secondary winding passes through the usual rectifier and choke circuits 35 and 36, respectively, as is well known in the art.

During operation, the power switch 29 is closed, following which the push-button 23 is pressed. Current flows through the coils 18-21, to create a degaussing field operative upon the cathode ray tube 12, the coils being formed of a wire which produces resistive heating, as well as magnetic lines of force within the core. Current is induced in the delay coil 24 which energizes the relay 27, and moves it to a first position, wherein latching contacts 28 are closed, thus eliminating the need for maintaining constant pressure upon the push-button 23. As the core 11 becomes heated, the obtainable flux gradually diminishes, and the amount of current induced in the delay coil 24 correspondingly diminishes to a point where it no longer maintains the relay 27 in the first mentioned position. The relay then moves under resilient action to a second position, following which the second contacts 34 complete the circuit through the secondary winding 33 to allow plate voltage to flow to the tubes of the receiver, and ultimately to the cathode ray tube.

The degausser will then remain inoperative until the receiver is again switched off by means of the switch 29, and the cycle may be repeated as often as necessary.

Turning to the second embodiment illustrated in FIG- URE 2, to avoid needless repetition, certain of the parts corresponding to those of the first embodiment have been designated by similar reference characters with the additional prefix 1.

The second embodiment of the invention difiers from the first embodiment in the elimination of the auxiliary member 17, and the substitution of a thermostatically controlled switch 39 including a heater coil 40 which performs the function of the relay 27. In this embodiment, the use of resistive heating in the coils 118, 119, and 121 is not required. To simplify construction, the coils 118-121 are operated at a higher voltage than in the first embodiment, and in the same circuit with the plate voltage.

In the third embodiment, again to avoid needless repetition, parts corresponding to those of the first embodiment have been designated by similar reference characters with the additional prefix 2.

In the third embodiment, a resistance heater 44 is placed in parallel with the secondary winding 233, and the coils 218-221 are also connected in parallel with the plate vlotage. When the switch 229 is closed, current is shorted through the resistance heater 44, the heating output of which is used to heat the core 211. As the heater 44 becomes hot, its resistance increases, with the result that current flows in greater degree to the plates of the tubes of the receiver.

In each of the three embodiments, the heating of the degaussing core causes a progressive reduction in flux to a minimal degree, following which the plate voltage becomes operative.

We wish it to be understood that we do not consider the invention limited to the precise details of structure shown and set forth in this specification, for obvious modifications will occur to those skilled in the art to which the invention pertains.

We claim:

1. A television degaussing means comprising magnetic means surrounding the face of a cathode ray tube, said magnetic means including a core formed of material exhibiting thermomagnetic properties, at least one coil surrounding said core, an alternating current source powering said coil, and means for progressively heating said core to proportionally diminish the magnetic flux output with increase in temperature.

2. Structure in accordance with claim 1 in which said core serves as said heating means.

3'. Structure as set forth in claim 2 in which said core includes an auxiliary segment, a delay co'il surrounding said segment, a relay powered by said coil, and contacts on said relay controlling flow of current to said cathode ray tube.

4. Structure in accordance with claim 3 including a power transformer having first and second windings having filament and plate voltage outputs, said relay controlling said plate voltage output.

5. Structure in accordance with claim 1 in which said core is formed of an alloy of approximately 30% nickel and the remainder iron.

No references cited.

10 JAMES W. LAWRENCE, Primary Examiner.

V. LAFRANCHL Assistant Examiner. 

1. A TELEVISION DEGAUSSING MEANS COMPRISING MAGNETIC MEANS SURROUNDING THE FACE OF A CATHODE RAY TUBE, SAID MAGNETIC MEANS INCLUDING A CORE FORMED OF MATERIAL EXHIBITING THERMOMAGNETIC PROPERTIES, AT LEAST ONE COIL SURROUNDING SAID CORE, AN ALTERNATING CURRENT SOURCE POWERING SAID COIL, AND MEANS FOR PROGRESSIVELY HEATING SAID CORE TO PROPORTIONALLY DIMINISH THE MAGNETIC FLUX OUTPUT WITH INCREASE IN TEMPERATURE. 